IMO, there is so many different ways to answer that depending on your goals. If you are trying to add muscle mass, then 2 days a week probably isn’t going to be significant enough to do that or at least notice any real gains. Of course that probably depends on the quality/type of lifting you’re doing. If you are just trying to throw in some weight training to augment your Tri training, I would say that you will be perfectly fine with 2 days a week (that’s what I do). If the latter is the case, I would recommend upping the reps and lowering the weight.

+1 that there’s a million different answers. Will you lose muscle mass if you decrease the amount of time spent lifting and increase the amount of time you spend on cardio activities? Most likely.

But will you be focusing on functional muscle capability and building strength and flexibility in those muscles and joints that you use most for this sport as opposed to building for just aesthetic reasons? Yes. There are a number of resources for the types of weight lifting exercises to do that supplement tri training.

Like others have said, it really depends on what your doing in the gym. During the season I only lift twice a week. One day I emphasize arms/back and the other is chest/core. But I do pull-ups, chin-ups, and other body weight exercises almost every day. If you have time time to lift three times a week and still get in solid S/B/R that’s awesome.

Can you make gains on lifting twice a week? Yes, but you would have to come up with a specific lifting regimen that incorporates complete muscle movements. (no machines) Im no physio, but that is my two cents. Personally, I’d rather bag the third lift and get some more pool time in.

Its really gonna come down to what your parents gave ya(genes). I can def make gains on 2x a week but my friend would have give up running to get any bigger. Jbird’s on the spot with lifting with freeweights (bench, military, squat, etc). Incorporate a pushup, pullup, etc plan too.

And don’t discount swimming! It’s pretty good for keeping strength. All in all though, you may have to reimagine what you consider an acceptable amount of strength while triathlon training.